System for alternately recording and controlling



H. C. PARKER SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING FiledSept. 9. 1926 4 Sheets-Sheet 1 7/70/22" IIMMZ I N V EN TOR. 7 emu IATTORNEY.

May 27, 1930. H. c PARKER 1, 9

SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed s t. 9, 1926 4Sheets- Sheet 2 '1 uuuuuunnunnn eooooooooooe a. N INVENTOR.

By 7 A mdw 2 ATTORNEY.

H. C. PARKER Mai 27, 1930.

SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed Sept. 9, 1926 4Sheets-Sheet 5 IN VEN TOR.

% WM'ED K; ATTORNEY.

May 27, 1930. H. c. PARKER 1,759,995

I SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed Sept. 9, 1926 4Sheets-Sheet 4 N Y fi I N VEN TOR BY 1% a GMQ,

762. ATTORNEY.

Patented May 27, 1930 UNITED STATES PATENT OFFICE HENRY O. PARKER, OFPHILADELPHIA, PENNSYLVANIA, AS SIGNOR TO LEEDS & NOR- THRUP COMPANY, OFPHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA SYSTEM FORALTERNATELY RECORDING AND CONTROLLING Application filed September 9,1926. Serial No. 134,427.

a My invention relates to a system for alternately recording andcontrolling the magnitudes of a condition, suchas theelectro-motiveforce, impedance, ion concentration. or

'5 conductivity of an electrolyte, temperature,.

etc. i In accordance with my invention, periods for recording andcontrolling, of any suitable relative lengtl s,alternate with eachother. During a recording period, the varying magnitude of the conditionis recorded, andduring a control period there i's'substituted for theion concentration cell, conductivity cell,

resistance, impedance or othenmeans for exhibiting "varlat ons of themagnitude 1nvolved, another device, as a source of electro-.

for the control to take effect; and more particularly in accordance withmy invention, this time lag, which is constant after having once beenempirically determined, is equal to the sum of the recording and controlperiods, and the control period is preferably a small fraction of therecording period.

Further in accordance with my invention, the change in the rate ofapplication of the agent which effects change in magnitude of thecondition is proportional to the difference between the actual magnitudeof the condition and the desired magnitude of the condition at the timeof inception of the control or change in rate of application of theagent; and more particularly in accordis effected by limiting thedeflections of a galvanometer, which controls the control mechanism, tosubstantially constant magnitudes which are independent of the extent ofdeparture of the actual magnitude of the ance with my invention, thisproportionality condition from the desired magnitude, but the durationof the deflection is dependent upon the aforesaid departure of theactual from the desired magnitude of condition.

My invention resides in a method and apparatus of the characterhereinafter described.

Foran understanding of my method, and for an illustration of some of thevarious forms my apparatus may take, reference is made to theaccompanying drawings, in which:

Fig. 1 is a diagrammatic View of one of the circuit arrangementsutilized in accordance with my invention.

Fig. 2 is a perspective view of recording and control mechanismembodying my invent1on.

Fig. 3 is a fragmentary elevational view of switches and their actuatingor control mechanism.

Fig. 4 is a sectional view, partly in elevation, of a control valve.

-Fig. 5 is a sectional view, partly in elevation, on the line 55 of Fig. 4.

Fig. 6 is a fragmentary sectional View taken'onthe line 66 of Fig. 5.

Fig. 7 is an elevational view, partly in section, of a modified form ofvalve structure.

Fig. 8 is a fragmentary elevational view, on enlarged scale, of aportion of the recording and control mechanism.

Fig. 9 isa top plan- View of the structure shown in Fig. 8.

Fig. 10 is a fragmentary sectional View on the line 1010 of Fig. 8.

Fig. 11 is a perspective view of an adjustable abutment.

Fig. 12 is a diagrammatic View of a modified circuit arrangementutilizable in accordance with my invention.

Fig. 13 is a fragmentary View, partly in section, of structureutilizable in temperature control in accordance with my system.

Fig. 14 is a diagram of a complete cycle of control illustratingalternate recording and control periods.

In Fig. 1 there is illustrated diagrammatically a system for applying towater, for example, Whose rate of flow may vary, another material, suchas acid, to procure a product comprising a mixture of water and acid inpredetermined proportions, or having a predetermined ion concentration.

The condition whose magnitude varies is,

for example, the hydrogen ion concentration of the mixture, and theagent applied at progressively varying rate for maintaining a desiredhydrogen ion concentration is the aforesaid acid. The magnitude of theion concentration is represented by an electromotive-force produced by ahydrogen ion cell which is a source of variable electro-motiveforceincluded in a balancing circuit, such as a potentiometer circuit,including a galvanometer whose deflections control suitable mechanismfor in turn controlling a valve upon whose extent of opening depends therate of application of the acid. It will, therefore, be understood thatFig. 1 represents not only a preferred application of my invention, butalso generically the application of any suitable agent for varying themagnitude of any condition during periods which alternate with periodsfor recording the variations in magnitude of the condition.

Briefly, in Fig. 1, water (which term includes generically any othermaterial) is delivered through the pipe W, controllable by the manuallyoperable valve '0, into the mixing tank T, into which is delivered acid(which term includes generically any other suitable material or agent)through the pipe A controllable by the manually operable valve 42 and bythe control valve V operable in opposite directions by the reversibleelectric motor N during the hereinafter described control periods. Themixture is discharged to any suitable region or point of use through thepipe D, controllable by the manually operated valve Q2 A continuoussample or side stream of the 4 resultant mixture is conducted throughthe pipe d, controllable by the manually operable valve '0 to andthrough the cell H, from which it is discharged through the tube (Z Thecell H may be a hydrogen ion cell of any suitable character, to whosepositive and negative electrodes are connected, respectively, theconductors p and n. The cell H constitutes a source ofelectro-motive-force, vary ing in magnitude with variations in magnitudeof the condition to be controlled, in a potentiometer circuit P withwhich co-acts the galvanometer G having, as indicated in Fig. 2, theneedle or pointer 19 actuated by the movable or deflecting system orcoil 20 for controlling the mechanism which alternately operates as arecorder and a controller. Both the recording and controlling operationsare effected by and in accordance with the angular movements of theshaft 10. For recording, the shaft 10 controls movement of the marker orpen B transversely of the continuously moving record sheet or paper S.For controlling, the shaft 10 rotates the disk G carrying the contactswand b,

which, in cooperation with the stationary or adjustable contact 0,control the aforesaid valve-actuating motor N.

The control and recording mechanism may be of any suitable character,and may, for example, and preferably, be generally of the characterdisclosed in prior Letters Patent to Leeds No. 1,125,699, January 19,1915.

Briefly, this mechanism, Fig. 2, comprises the electric motor M whoseshaft 1 drives at substantially constant speed the Worm 2 meshing withand driving the gear 3 secured upon and driving the shaft 1. Pivotedupon a horizontal axis adjacent its upper end is a lever 5, upon whichthere is pivoted on a horizontal axis the arm 6, on each end of which isa shoe of cork or the like frictionally engaging the rim 8 of the clutchdisk 9 secured upon the aforesaid shaft 10. Secured upon the shaft l isa cam 11, which periodically engages the lever 5 and moves it outwardlyaway from the disk 9 in opposition to a spring, not shown, therebylifting shoes 7 free from the rim 8, the spring returning the shoes intoengagement with the rim after predetermined rotation of the cam 11. Uponthe shaft 4 is secured asecond cam 12 which, after cam 11 has lifted theshoes 7 from rim 8, actuates the end of finger 13 on the lower end ofarm 14 secured at its upper end to the member 15 pivoted at 16. Upon theframe 15 is secured the member 17, whose upper edge 18 is inclined andincreases in height from the center toward each side. Disposedimmediately above the edge 18 is the aforesaid needle or pointer 19 ofthe galvanometer Gr. Deflections of the needle 19 are limited by theabutments 15 Figs. 2, 8, 9, 10 and 11, disposed on opposite sides of theneedle 19 and secured to the member 15 by screws 15 extending throughslots 15 in the lugs 15,

to which the abutments 15 are secured or with which they are integral.These limiting lugs 15 have a purpose and function hereinafter referredto.

Directly above the needle 19 and beneath which it normally freely swingsare the edges 21, preferably. straight and horizontal, on the lowersides of the members 22, 22, pivoted at 23, 23 and extending toward eachother, leaving a gap of sufficient width between their inner nds toallow the free entry of the needle 19 when in balanced, Zero or midposition. The needle 19 normally swings freely between the edge 18 ofmember 17 and the lower edges 21 of the members 22. Upon the members 22are the downwardly extending arms 24, 2 1, drawn toward each other bythe spring 25. Attached to the lower end of lever 5 is the triangularplate 26 carrying the pins 27 and 28, with which co-act the lower endsof the fingers 24:. At opposite ends of the arm 6' are the ears or lugs29, 29, adaptedto be engaged by the cams 30, 30, similarly shaped andsimilarly positioned and secured upon the shaft 4.

As well understood, the deflections of the galvanometer needle 19 causerotations of the shaft 10 to extents and in directions proportional toor dependent upon the extents and directions of deflections of theneedle 19; by application of the deflection-restricting lugs 15,however, the movements of the shaft 10 are substantially equal so longas the needle 19 is in engagement with either lug 15, but the directionof movement of the shaft 10 still depends upon the direction ofdeflection of the needle 19.

Secured upon the shaft 10 is the aforementioned disk G, whose angularposition upon the shaft 10 is adjustable by means of the set screw 31threaded through the hub 32 of the disk C, thereby determining theposition of the gap between the motor control contacts a and Z) withrespect to the contact a, mounted on arm 47.

Upon the shaft 10 is secured the grooved pulley 33, around which passesthe cord 34, passing over idler wheels 35, for moving the aforesaidmarker on pen B transversely of the record sheet S, which latter isstored upon a roll 36 and passes over the sprocket roll 37 driventhrough suitable gearing from the shaft 4.

Upon the disk E, which is secured upon the shaft 10 in any suitableangular adjustment thereon by the screw 38, is the resistance R, withwhich co-acts the stationary contact 39 to constitute a slide wireresistance of the aforementioned potentiometer P, Fig. 1. Secured uponthe shaft 40 is the adjustably mounted and manually operable dial orknob 41, bearing suitable graduations in any suitable units, aselectro-motive-force, for the system of Fig. 1. WVith the markings uponthe member 41 co-acts the stationary index 42, whereby the member 41 andshaft 40 may be rotated to or set in any predetermined positioncorresponding with the desired magnitude of the condition to becontrolled. Upon the shaft 40 is adjustably secured a disk F, upon whichis disposed the resistance R with which co-acts the stationary contact43 to constitute a second slide wire of the potentiometer P, of whichthe resistances R and R are in parallel with each other. Upon the shaft40 is secured the gear 44, meshing with the gear 45 loosely bearing uponthe shaft 10 and carrying the bracket 46, preferably of insulatingmaterial, upon which is secured the conducting arm 47 which carries theaforesaid motor-control contact a co-acting with the contacts a and 5upon the disk C.

The dial 41 and slide wire resistance R. are so mounted that when thecontact 43, operating on slide wire R is at the same potential as thatof the contact 39, operating on slide wire R, the index 42 points to apotential value on dial 41 which corresponds to the potential indicatedon the recorder scale. When this adjustment is made, the disk C, mountedupon the shaft 10, is simultaneously adjusted so that the contact 0falls midway between the contacts a and Z).

Reverting to Fig. 1, the contact 0 connects through the switch I, whenclosed, with the conductor 48 of a current supply circuit, for example,of the direct current type, whose other conductor 49 connects with oneterminal of the armature 5O ofthe reversible motor N, having the twofield windings 51 and 52 brought into series with the armature 50,respectively, through the contacts a and Z; for effecting rotation ofthe motor shaft 53 in the one direction or the other. The shaft 53,through suitable reducing gearing, ro-

tates the stem 54 of the valve V.

The potentiometer P comprises the aforesaid slide wire R through whichcurrent of predetermined magnitude from the battery 6, as determined bythe rheostat f, is passed.

During the recording period the contact 39, bearing upon the resistanceR, is connected through the switch J with one terminal, as the positive,of the cell H through the conductor 19, and the negative terminal, forexample, through the conductor a, connects to the galvanometer G andthence through the switch L, when in its upper position, and thencethrough the switch K, when in its upper position, with one terminal ofthe resistance 9 in series with the aforesaid resistance R. During therecording period the contact 43 of the slide wire R on disk F, is out ofcircuit, and the system comprises then a simple potentiometer systemproducing upon the sheet S by the marker B a record of the potentialdifferences across the electrodes of the cell H depending in turn uponthe variations in the hydrogen ion concentration in the mixture of acidand water discharged through the pipe D.

The switch L, Fig. 1, is shown also in Figs. 2 and 3 as actuated orcontrolled by the cam 55 engaged by the cam follower 56 carried upon theswitch blade L. The face of the cam 55 is of such angular extent and sopositioned upon the shaft 4 that the switch L is in its lower position,Fig. 1, during each period that the galvanometer needle 19 is held orclamped between the members 17 and 22, thereby opening the circuit ofthe cell H, preventing useless withdrawal of current therefrom duringthe periods in which the galvanometer needle is retrained by theclamping members, and thereby reducing the amount of polarization whichtakes place in the cell H due to withdrawal of current therefrom whileits circuit is closed. When the switch L is is in its lower position,opening the circuit of the cell H, it shunts the galvanometer Gr throughthe resistance h,

which may be of suitable magnitude for damping oscillations of thegalvanometer upon release of its needle and before the circuit of thecell H is again closed by the switch L at its upper position.

The switches I, J and K are mechanically connected by an insulatingmember 57, Figs. 2 and 3, constituting a follower for the cam 58 securedupon the shaft 59 driven through reducing gearing 60, 61 by the shaft 4.The relatively slow speed of rotation of the shaft 59 introduces a timelag, effecting delay of ac tion of the switching mechanism by the cam 58for a period which is the sum of the control and recording periods. Thecontrol period is preferably the shorter, and may be of the order ofone-eighth the duration of the recording period. This ratio of therecording and control periods is determined by the contour of the cam58, which, when the follower 57 is upon the cam surface of largerdiameter, holds the switches I, J and K closed in the positionsindicated in Fig. 1 for recording. WVhen the follower 57 passes off onto the cam surface of lesser diameter, a control cycle or period isinstituted, and the switches I, J and K move against their lowercontacts, Fig. 1.

During a control period, the switch I, in effect a motor control switch,is brought into communication with the control contact 0, to permit thecontacts a and b to cause rotation of the motor N in the one directionor the other. Similarly, during a control period, one terminal of thegalvanometer G communicates through the switch J with the contact 39 inengagement with the potentiometer resistance R, and the other terminalof the galvanometer connects through the periodically actuated switch Land the switch K with the contact 43 in engagement with the second slidewire resistance R This shifting of the switches J and K into engagementwith their lower contacts, Fig. 1, in effect cuts out for the controlperiod, during which polarization ceases, the source ofelectro-motive-force or cell H, and connects the galvanometer G, througha suitable resistance 2', across the contacts 39 and 43,substituting-for the electro-motive-force of the cell H, or genericallyfor the electrical effect representative of the changes of the magnitudeof the condition involved, a potential difference between points on theslide wires R and R determined by the manual setting of the disk F, Fig.2. In this way there is in effect substituted for theelectro-motiveforce of the cell H an auxiliary electro-motive-force,whose value is equal to or representative of the voltage across theterminals of the device H corresponding with or representative of thedesired magnitude of the condition.

By adjusting the knob or dial 41 to position corresponding with thedesired magnitude of the condition to be controlled, there is in effectset up in the potentiometer circuit a reference voltage, correspondingto the desired magnitude of the condition, and the control is theneffected with regard to the manually selected electro-motive-forcerepresenting the desired magnitude.

If at the beginning of a control period the ion concentration of themixture discharged through the pipe D is at the desired magnitude, thecontrol mechanism will not operate, because the contact 39 will havebeen moved along the slide wire R during the preceding recording periodto a point corresponding with the desired magnitude, and in so doing thedisk C, mounted on the same shaft 10, will have rotated to such aposition that the contact 0 is midway between the contactsa and b. Themotor circuit is, therefore, broken at this point; and there willtherefore be no difference of potential between the contacts 39 and 43.If, on the other hand, at the beginning of a control period, that is, atthe end of a recording period, the ion concentration is at some otherthan the desired magnitude, the shaft 10 of the structure shown in Fig.2 will have rotated the resistance R with respect to the contact 39, inproducing the record up to the end of the recording period, to such aposition that there is then a difference of potential between thecontacts 39 and 43 representative of the departure of the then magnitudeof ion concentration from the desired magnitude. During the rotation ofthe shaft 10, the disk 0 becomes rotated in respect to contact 0,thereby causing engagement of contact 0 with contact a; or 6 -ac cordingto whether the magnitude being measured is below or above the desiredvalue. WVhen the key I, Fig. 1, is then closed at the start of a controlcycle, the motor circuit is completed and the valve V starts opening orclosing according to whether the magnitude is above or below the desiredvalue. At the same time the recorder starts to balance at the potentialrepresented by the setting of dial 41, Fig. 2, and hence the shaft 10start-s to rotate in such a direction as is required to place contact 0midway between contacts a and Z). As soon as the contact 0 disengagesfrom contacts a or b, the motor circuit is broken. In this manner theangular displacement of the valve V is proportional to the time requiredfor the recorder to come to balance at the potential-.

of rotation in the same direction, the number of these movementsdepending upon the duration of the deflection of the needle 19, whichduration is dependent upon or proportional to the magnitude of thedeparture at the beginning of the control cycle of the actual from thedesired ion concentration of the material in the discharge line D. Thelimitation of the deflection of the needle 19 by the abutment structure15 increases the time for moving the resistance R with respect to itscontact 39 through a given or unit angle. There is accordingly effectedan increase of opening of the valve V for a given displacement ordeparture of the ion concentration from the desired magnitude. lVith thevalve-actuating motor N operating at a substantially constant speed andwith a given gear ratio between the motor shaft and the valve stem 54,the limitation of the deflection of the needle 19 by the abutmentstructure 15 has the effect that for a given displacement or departurefrom the desired concentration the motor is caused to operate for alonger period. For example, adjustment of the abutments 15 towards thezero or null position of the needle to half distance requires thevalve-actuating motor N to run twice as long, so effecting twice thechange in the extent of rotation of valve V.

The valve V is not actuated from closed position to open, or vice versa,but its aperture or opening is progressively or gradually changed byrotation of the stem 54. This is effected by structure of any suitablecharacter, an example of which is illustrated in Figs. 4, 5 and 6, inwhich the plug 54*, ro-. tated by the stem 54, is provided with a'wall54 having a series of ports or holes 54 disposed in a suitably curvedpath, whereby the rate of change of effective valve opening graduallyvaries with rotation of the plug 54 about its axis. 4

In Fig. 7 a generally equivalent arrangement is shown wherein in theplug 54 there is provided a tapered opening 54 producing generallysimilar effect to that described in connection with Figs. 4 and 5.

The operation as above described effects a control of the rate ofapplication of the agent, causing change in the magnitude of thecondition involved, which is proportional to the difference between thedesired magnitude of the condition and the actual magnitude at theinception of a control period. This proportionality is dependent uponthe limitations of the deflections of the galvanometer needle 19 byabutments 15 tosubstantially constant magnitudes which are independentof the extent of the departure of the actual from the desired magnitudeof the condition, but the duration of the deflection of the needle 19 isdependent upon the magnitude of that departure, and so keeps thevalve-actuating motor N in operation and varies the opening of the valveV for a period which is dependent upon the departure of the actual fromthe desired magnitude of the condition.

At the end of a control period, the cam 58 actuates the switches I, Jand K. to restore them to their recording position indicated in Fig. 1,whereupon the motor circuit is additionally broken at the switch I, anda record is produced on the sheet S of the variations in the magnitudeof the ion concentration 00- curring during the recording period.

The gearing 60, 61 drives the cam 58 so slowly that there is effected atime lag to permit the control to take effect, that is, to allow timeafter change of rate of admixture of acid for the effect of theadmixture to make itself felt as regards its influence upon the cell H.This time lag is dependent upon the speed of the motor M and the extentof the reduction of speed effected by the reducing gearing intermediatethe motor shaft and the shaft 59. The time lag is accordingly constant,but may be readily adjusted by changing the gear 61. It is equal to thesum of the recording and control periods, and the control period ispreferably a small fraction, as, for example, one-eighth of therecording period.

While recording and control of ion concentration have been morespecifically re- 5 ferred to above, it will be understood that the theremay be mentioned temperature; for example, the temperature within afurnace 0, Fig. 13, produced by combustion of gas delivered through thepipe 62 through the valve V to the burner 63, which latter may be themain burner or an auxiliary burner. A thermocouple Q is disposed withinthe furnace,

partaking of the temperature thereof. and

producing an electro-motive-force corresponding with the temperature.The thermo-couple Q may be substituted for the cell H in the arrangementof Fig. 1, and the motor N then controls the gas supply valve V.

In Fig. 12 the mixture of acid and water, for example, is againcontrolled by the valve V. Immersed in the mixture in the tank T are theelectrodes and 7c of a conductivity cell, the resistance between theelectrodes j and 7c varying with changes in concentration of the acid inthe mixture. The cell is included in one arm of a Wheatstone bridge, intwo R, mounted upon the disk E of Fig. 2. With the resistance 69becomesthe source of alternating current in the second conjugateconductor 71 connected between the conjugate points 7 2 and 7 3 of theWheatstone bridge. During a recording period, in the system of Fig. 12,switches I, J and K are in their upper positions as indicated, and, asindicated in Fig. 2, they are actuated or controlled by the cam 58. Inthe recording position the switch I is open, thereby preventingenergization of the valve-controlling motor N. The switch J is closedagainst its upper contact, thereby completing the arm of the bridge,containing the resistance 9, between the points 65 and 72. The switch Kin its upper position completes the arm of the bridge, containing thecell j, is, between the points 65 and 73.

At the end of a recording period the cam 58, Fig. 2, shifts the switchesI, J and K into engagement with their lower contacts, the switch Ithereby closing the circuit to the motor control contact 0. The switch Jnow includes between the conjugate point 7 2 and the conjugate point orcontact 43 an arm of the bridge including the resistance 1" and aportion of the slide wire R in substitution for the resistance 9. Andthe switch K includes between the conjugate point 73 and the conjugatepoint 43 a resistance 8, and a portion of the slide Wire R insubstitution for the cell 9', la. Between the arms comprising theresistances r and s is the slide wire resistance R disposed upon thedisk F, Fig. 2, and its position with respect to the contact orconjugate point 43 is set or determined by hand, by operation of thedial or knob 41. The position of the contact 43 upon theresistance R isso chosen that the portion= of the resistance R to the right of theconjugate point 43, plus the resistance of s in the same arm, causes thebridge to balance andlh'lence causes contact 39 to occupy the sameposition on slide wire R as is caused, during the recording period, bythe resistance of the 'cell j, 70, when the concentration of theelectrolyte in the tank T is of the desired magnitude. 1

At the inception of a control period, therefore, the coil 20 of thegalvanometer will deflect only when there is a difference of potentialbetween the conjugate points 39 and 43, and this occurs only when at theend of a recording period the contact 39 is on such point of theresistance R as corresponds with a magnitude of concentration differingfrom the desired magnitude. During the control period, the apparatusoperates as heretofore described in connection with Figs. 1 and 2,causing a control by disk O of the motor N, and in turn of the valve V,and of the application of acid at such rate and for such time as torestore the concentration to or towards the desired magnitude, which,when reached, will cause a balance of the bridge, Zero deflection of thegalvanometer coil 20, and the cessation of operation of the motor N,since the contact 0 is again in the position between the two contacts aand b.

The operation during such control period is generally of the characterhereinbefore described in connection with Figs. 1 and 2. The time lag isprovided, the recording period is relatively longer than the controlperiod, and the abutments 15 again have the same purpose and result.

In the system of Fig. 12 again, periods of recording alternate withthose of control, and in shifting from recording to controllingoperations there is substituted for the device producing during therecording period an effect representatlve of varlatlons of the magnitudeof the condition, another device pro-' ducing an effect representativeof the desired magnitude of the condition, and the control effected isproportional to the departure of the actual from the desired magnitudeat the inception of the control period.

Fig. 14 illustrates graphically the operation of the mechanism inalternately recording and controlling ion concentration or othercondition. Base line XX represents the desired predetermined or standardvalue with respect to which the condition is to be controlled. Assumingthat ordinates above and below the base line represent degrees of highand low concentrations respectively, the action of the control mechanismin moving from X to X results in movement of valve V to a positionpermitting less flow of acid 7 to the main tank T. It is thereforeapparent that change in rate of flow of the agent controlling theconcentration depends upon the time required for control disc C to movebetween positions representative of X and X respectively. When controldisc 0 reaches point X it will be in the position indicated in Fig. 1wherein contact 0 is in neutral position for interrupting the motorcircuit.

Thus it will be noted thatthe extent of movement of valve V is notdependent on the length of time switch I is closed, but on the length oftime required for contact 0 to reach neutral position on disc 0. Byproviding adjustable stop members 15" to limit deflections ofgalvanometer pointer 19, movement of control disc C through clutchmember 6 may be effected in steps of different magnitudes. The number ofsuch steps per unit of time remains constant as the speed of motor M issubstantially constant, so the time required for contact 0 to reachneutral position may be considered as depending on the magnitude of theindividual steps of clutch 6.

When cam 58 has determined the length of the control period, switches Jand K operate so as to balance the bridge or potentiometer withreference to the true instead of the desired condition. The clutch willthen move pen-controlling disc 33 frompositionY toY and continuerecording to point Y when the control period will again take place.There.- upon valve V again closes to an extent dependent on thedeparture of the condition from its predetermined standard, only in casehowever that the limits of deflection of pointer 19 are maintainedconstant.

A suitable ratio between the duration of the recording and controlperiods may be effected by proper design of cam 58, as previouslyexplained, so that the condition will have sufficient time to vary inresponse to the control agent between control periods.

As previously brought out, the time lag, which is equivalent to the sumof a control and recording cycle, may be varied by changing gearing 61which drives switch actuating cam 58. The advantage of changing the timelag is readily apparent where a greater change in rate, for instance, ofapplication of the control agent is desired. In such a case, therelative duration of the recording period could not be appreciablydecreased for a given time lag as the full effect of the control agentwould not be recorded before the next control cycle began. By extendingthe time lag however, the control and recording periods may have thesame relative duration, while permitting an appreciable change in therate of application of the control agent.

WVhile there has been specifically described a conductivity cell in anarm of the bridge, it will be understood that any other suitable devicefor any suitable purpose may be uti lized in lieu thereof. For example,as indi cated in Fig. 13, there may be disposed in the furnace O athermometer resistance U, which may be utilized in a bridge of thecharacter indicated in Fig. 12 in substitution for the cell 7', is, inwhich case during the control period the sum of the resistance 8 andthat portion of the resistance R to the right of the contact 43 willcause the bridge to balance at a point identical to that caused by thethermometer resistance U at the desired temperature.

l/Vhat I claim is:

1. Thameth gdiwhich comprises producing an effect viiiiying inaccordance with variation of the magnitude of a condition, and producingin successive periods a record of variation of the magnitude during saidperiods, and during shorter periods alternating with said periodscontrolling the application of an agent for controlling the magnitude ofthe condition.

2. The method which comprises producing an effect varying in accordancewith variation of the magnitude of a condition, producing a record ofthe variation, substituting for said effect an effect representative ofa desired magnitude of the condition, and controlling the application ofan agent for varying the magnitude of the condition in accordance withthe difference between the magnitudes of said effects.

3. The method which comprises producing an effect varying in accordancewith variation of the magnitude of a condition, producing a record ofthe variation, substituting for said effectan effect representative of adesired magnitude of the condition, and controlling the application ofan agent for varying the magnitude of the condition in accordance withthe difference between the magni tude of said second named effect andthe magnitude of said first named effect at the termination of therecording period.

4. The method which comprises producing an effect varying in accordancewith variation of the magnitude of a condition, producing a record ofthe variation, substituting for said effect an effect representative ofa desired magnitude of the condition, controlling the application of anagent for varying the magnitude of the condition in accordance with thedifference between the magnitude of said second named effect and themagnitude of said first named effect at the termination of the recordingperiod, alternating the periods of record production and control, andcausing the recording periods to vary in duration from the controllingperiods.

5. The method which comprises producing an effect varying in accordancewith variation of the magnitude of a condition, producing a record ofthe variation, substituting for said effect an effect representative ofa de sired magnitude of the condition, and controlling the applicationof an agent for varying the magnitude of the condition in proportion tothe difference between the magnitude of said second named effect and themagnitude of said first named effect at the termination of the recordingperiod.

6. The method which comprises producing an effect varying in accordancewith variation of the magnitude of a condition, producing a record ofthe variation, substituting f6? said effect an effect representative ofa desired ma nitud e pf the cogdition, controlling the application ofan"agent for varying the magnitude of the condition in proportion to thedifference between the magnitude of said second named effect and themagnitude of said first named effect at the termination of the recordingperiod, alternating the periods of record production and control, and

causing the recording periods to vary in duration from the controllingperiods.

7 In a system of recording and control, a deflecting member, a movablestructure the extents and directions of whose movements are controlledby said deflecting member, recording and control structures controlledby said movable structure, and means for controlling said recording andcontrol structures alternately.

S. In a system of recording and control, a deflecting member, a movablestructure the extents and directions of whose movements are controlledby said deflecting member, recording and control structures controlledby said movable structure, means for cont-rolling said recording andcontrol structures alt-ernately, and means for causing the periods ofcontrol of the recording structure to vary in duration from the periodsof control of said control structure.

9. In a system of recording and control, the combination with agalvanometer, of a circuit controlling it in accord with varia tions inmagnitude of a condition, a movable structure the extents and directionsof whose movements are controlled by said galvanometer, recording andcontrol mechanisms controlled by said movable structure, and means foreffecting alternate control of said recording and control mechanisms.

10. In a system of recording and control, the combination with agalvanometer, of a circuit controlling it in accord with variations inmagnitude of a condition, a movable structure the extents and directionsof whose movements are controlled by said galvanometer, recording andcontrol mechanisms controlled by said movable structure, means foreffecting alternate control of said recording and control mechanisms,and means for causing the periods of control of the recording mechanismto vary in duration from the periods of control of said controlmechanism.

11. In a system of recording and control, the combination with agalvanometer, of a balancing circuit controlling it, means in saidcircuit responsive to variation in mag nitude of a condition, a movablestructure controlled by said galvanometer, recording mechanism and meansfor balancing said circuit controlled by said movable structure, meansfor substituting in said circuit for said first named means meansproducing an effect representative of a predetermined desired magnitudeof the condition, and control mechanism controlled by said movablestructure while said last named means is in cir cuit.

12. In a system of recording and control, the combination with agalvanometer, of a balancing circuit controlling it, means in saidcircuit responsive to variation in magnitude of a condition, a movablestructure controlled by said galvanometer, recording mechanism and meansfor balancing said circuit controlled by said movable structure, meansfor substituting in said circuit for said first named means meansproducing an eflect representative of a predetermined desired magnitudeof the condition, control mechanism controlled by said movable structureWhile said. last named means is in circuit, and means for causing theperiods of control of the recording mechanism to vary in duration fromthe periods of control of said control mechanism.

13. The combination with a deflecting member, of a periodicallyoperating member adapted to engage said deflecting member, driving anddriven members, means for setting the driving member with respect to thedriven member in response to engagement of said deflecting member bysaid periodically operating member, means for thereafter actuating thedriving member to move the driven member, a marker controlled by saiddriven member, and abutment structure limiting the deflections of saiddeflecting member to small extents, whereby during the application ofdeflecting force to said deflecting member said driven member partakesofa series of short movements.

14:- The combination with a deflecting member, of a periodicallyoperating member adapted to engage said deflecting member, driving anddriven members, means for setting the driving member with respect to thedriven member in response to engagement of said deflecting member bysaid periodically operating member, means for thereafter actuating thedriving member to move the driven member, control mechanism controlledby said driven member, and abutment structure limiting the deflectionsof said deflecting member to small extents, whereby during theapplication of deflecting force to said deflecting member said drivenmember partakes of a series of short movements.

15. The combination with a potentiometer circuit, of a galvanometercontrolled thereby, a source of electro-motive-force in said circuitrepresentative of variation of the magnitude of a condition, and meanscontrolling said condition comprising means for substituting for saidsource a second source of electro-motive-force of fixed magnitude whosemagnitude represents a predetermined magnitude of the condition.

16. The combination with a potentiometer circuit, of a galvanometercontrolled thereby, a cell in said circuit producing anelectro-motive-:torce varying with variation of magnitude of ionconcentration, and means controlling said condition comprising means forsubstituting for said cell a source of electro-motive-force of fixedmagnitude representative of a predetermined magnitude of the ionconcentration.

17. In a control system the combination with a Wheatstone bridge, of agalvanometer deflecting when said bridge is unbalanced, an impedance inan arm of said bridge varying in magnitude in accordance with variationin magnitude of a condition to be controlled, and means controlling saidcondition comprising means for substituting for said impedance animpedance of fixed magnitude representing a predetermined magnitude ofthe condition.

18. In a control and recording system the combination with a WVheatstonebridge, of a galvanometer deflecting when said bridge is unbalanced, aconductivity cell in an arm of said bridge varying in resistance withvariation of composition of an electrolyte, and means controlling saidcondition comprising means for substituting for said cell an impedanceof flxed magnitude representative of a predetermined composition of saidelectrolyte.

19. The combination with a balancing circuit, of a galvanometercontrolled thereby,

. means in said circuit for producing an effect representative of thevariation of magnitude of a condltlon, means for substituting there-'for means producing a like effect representative of a predeterminedmagnitude of the condition, and recording and control mechanismsalternately controlled by said galvanometer to respectively recordvariations in the magnitude of the condition and to vary said magnitude.

20. The combination with a potentiometer circuit, of a valvanometercontrolled thereby, a source of electro-motive-force in said circuitrepresentative of variations of the magnitude of a condition, means forsubstituting for said source a second source of electro-motiveforcewhose magnitude represents a predetermined magnitude of the condition,and recording and control mechanisms alternately controlled by saidgalvanometer to respectively record variations in the magnitude of thecondition and to vary said magnitude.

21. The combination with a potentiometer circuit, of a galvanometercontrolled thereby, a cell in said circuit producing an electromotive-force varying with variation of magnitude of ion concentration,means for substituting for said cell a source of electromotive-force offixed magnitude representative of a predetermined magnitude of the ionconcentration, and recording and control mechanisms alternatelycontrolled by said galvanometer to respectively record variations in themagnitude of the ion concentration and to vary the ion concentration.

22. The combination with a Wheatstone bridge, of a galvanometerdeflecting when said bridge is unbalanced, an impedance in an arm ofsaid bridge varying in magnitude in accordance with variation inmagnitude of a condition, means for substituting for said bridge isunbalanced, a conductivity cell in an arm of said bridge varying inresistance with variation of composition of an electrolyte, means forsubstituting for said cell an impedance of fixed magnituderepresentative of a predetermined composition of said electrolyte, andrecording and control mechanisms alternately controlled by saidgalvanometer to respectively record variations in the composition ofsaid electrolyte and to vary the composition of said electrolyte.

24. The combination with a galvanometer, of movable structure whosemovements are controlled by said galvanometer, a control circuit,relatively movable contacts controlling said circuit, one of saidcontacts moving in unison with said movable structure, an electricaldevice afi'ecting deflection of said galvanometer, and means independentof said movable structure for adjusting said device and another of saidcontacts in unison.

25. The combination with a balancing circuit, of a galvanometercontrolled thereby, movable structure controlled by said galvanometer,electrical means in said circuit adjusted by said movable structure torebalance said circuit, a control circuit, contacts controlling saidcontrol circuit, one of said contacts moved by said movable structure,electrical means operatively related to said circuit for aflecting thedeflection of said galvanometer, and means for adjusting said last namedmeans and another of said contacts in unison.

26. methodof c ontrolnfor a physical, 11o

chemical,*""tliermal"or electrical condition", which consists ofbalancing an electro-motive-force representative of said conditionagainst an electro-motive-force representative of a predetermined ordesired condition for determining the degree of departure from the same,and v arying by steps the appllcationgjj an agent ,oiireagent forcorrecting said ndition, the rate of change of said application b e ngproportional to the degree of 1 departure of said condition from itspredetermined standard at the beginning of said control.

27. In a system for eflecting control of a condition with respect to apredetermined standard, electrical balancing means adapted to balance atpositions representative of the actual and desired conditionsrespectively, and mechanism controlled thereby for varying theapplication of an agent for correcting said condition at a rate which isproportional to the time required for said balancing means to move froma balance representative of the actual condition to a balancerepresentative of the desired or standard condition.

28. A system for eflecting control of a condition with respect to apredetermined standard comprising electrical balancing means responsiveto forces representative of the actual condition and its desired orpredetermined standard respectively, mechanism controlled thereby forvarying the rate of application of an agent or reagent for correctingsaid condition, said rate of variation being proportional to the degreeof departure of said condition from its predetermined standard at thebeginning of said control.

29. A system for effecting control of ion concentration of asolutionwith respect to a predetermined standard comprising electricalbalancing circuit, a deflecting member responsive to conditions withinsaid circuit representative of variations of said concentration from itspredetermined standard, a

control member movable through equal steps in response to deflections ofsaid deflecting member, and means governed by said control member duringa control period for varying flow or addition of a reagent forcorrecting said concentration at a rate which is proporboth actual anddesired states ofa condition under control, means for effecting controlof said condition while said mechanism is responsive to the desiredstate alternating with means for recording while said mechanism isresponsive to the actual state of said condition, means for maintaininga predetermined ratio between the duration of said control and recordingcycles, and means for varying the time lag of said system by varying theperiod representative of the summation of a recording and control cycle.

33. A system for effecting control of a condition with respect to apredetermined standard comprising electrical balancing means, mechanismperiodically controlled thereby for efl'ecting control of said conditionby varying the rate of application of an agent or reagent at a ratewhich is proportional to the duration of said control period, meansactuated in alternation with said mechanism for recording saidcondition, and means for varying the combined duration of a recordingand control cycle, thereby varying the time lag of said system.

HENRY C. PARKER.

tional to the extent of movement of said control member during saidperiod.

30. In a system for effecting control of a condition with respect to apredetermined standard, the combination with a balancing circuit, adeflecting member responsive to conditions therein, a member forcontrolling the rate of application of a control agent movable indirection and degree in accordance with the deflection of saidfirst-named memher, and adjustable means for limiting the deflection ofsaid first-named member within variable limits whereby said: controlagent may be applied over a variable period of time for a givendeparture of said condition from its normal standard.

31. In a system for eflecting control of a condition with respect to apredetermined standard, the combination with a balancing circuit, adeflecting member responsive to conditions therein, a member forcontrolling the rate of application of a control agent movable indirection and degree in accordance with the deflection of saidfirst-named member, and adjustable means for limiting the

